The need for home roofing insulation to save energy costs is an on-going concern in the roofing field. Conventional roofing and siding of the prior art includes the traditional wood shingles and siding, concrete and clay tiles, and asbestos shingles and metal siding. Most of these roofing materials require periodic maintenance to keep them in satisfactory condition. Another disadvantage of such roofing materials is that they are not inherently good insulators and thus require underlying auxiliary thermal insulation in the roof, ceiling or wall structure. While wood shingles are highly decorative, they have the disadvantage of having low fire-resistance and are often prohibited by fire regulations in some localities and almost universally impose increased costs for fire insurance. Concrete and clay tiles have the disadvantage of substantial weight, thus increasing the cost of the underlying structures. It has long been apparent, therefore, that a need exists in the art for light-weight, decorative, fire-resistant siding or roofing having good thermal insulating properties.
With the advent of plastics, much research has gone into adapting its use to the roofing industry. At first, such synthetics were applied in sheet form only for their water-resistant qualities, but more recently attention has been focused on polystyrene and polyurethane foams for their heat and sound-insulating characteristics. Probably the widest use of such foam, which is typically formed from a foamable polyurethane resin reaction mixture, is to apply it while in a liquid state by hose and spraying equipment directly onto a roof bed. This technique has proven itself to be very valuable for commercial building projects, but because of its cost, the fact that it is not very pleasing aesthetically, and the fact that it is only practical on relatively flat roofs, it is not generally used as a residential roofing medium.
Noting the desirable heat and sound-insulating qualities, the industry has worked with the thermosetting polyfoams in the form of boards or large rectangular sheets having opposite broad flat surfaces from one to two inches in thickness. Typically, foam boards are laid down over the roof deck, and then the foam boards sealed to prevent leaking. Also, protective layers are generally provided on the outer flat surface of the foam boards in order to lessen decomposition thereof when certain ones of the foam materials are exposed to wind, rain and sunlight. Unfortunately, not only is this technique very complicated and costly, but also the results leave much to be desired as to eye appeal. Accordingly, it has been found that this flat-type construction is not generally desired by home owners and is seldom used.
Over the years, in spite of the above approaches, the use of asphalt-based shingles as replacement for naturally occurring materials, such as wood and slate, in order to reduce the cost of roofing has become increasingly popular. In fact, a very large industry has been developed to produce roofing using asphalt-based materials. These products have become very popular because of their ease of use and relatively low cost as compared with the aforementioned wood and slate and as also compared with traditional man-made tile roofing. However, asphalt shingles absorb heat when exposed to sun, and thus, as with wood and slate shingles, asphalt-based also offer little in the way of insulation for the roofing structures of homes. The shingle heat radiates into attic spaces where high temperatures can increase the heat load on cooled spaces in the summer. But since asphalt shingles are used on the vast majority of residential houses, it is often identified as the product to have its thermal properties improved.
Conventional approaches have mainly used insulation materials lined across the entire shingle backs. While such a use of insulation can reduce the amount of heat that is transferred by the shingle through the deck into building attic spaces, asphalt shingles require a solid surface for their installation installed for best performance. Thus, since the entire bottom surface of such shingles are lined with a thick insulation layer, one row of shingles does not bond well to a subjacent row of shingles, as is the case with bare asphalt shingles. As a result, the shingles may not provide the good wind resistance that they might otherwise provide. Also, in many locations, asphalt shingles are not allowed to be applied directly to insulation without a nailable surface, such as exterior grade plywood or oriented strand board.